A conventional disc changer normally has a plurality of trays housed within a casing, with each tray arranged to carry an optical disc. In one known type, the disc changer includes a single selected tray or a main tray with a selected sub tray and by depressing an eject button the main tray carries the sub tray to move from a standby position within the casing to protrude outward to a disc exchange position for inputting or exchange of a disc. A disc can then be placed on the sub tray which, upon receiving a suitable signal, carries the disc together with the main tray into the standby position. At the standby position, the sub tray departs from the main tray to carry the disc to a storage rack within the casing which can hold a plurality of disc to be played. With this configuration, only one disc can be input or exchanged at a time, and to load a disc or replace a disc, each of the rest of the trays have to be ejected individually transported by the main tray. This can greatly inconvenience an end user since, more often than not, after keeping the discs inside the disc changer for a period of time, the user would not be able to remember the correct arrangement of the discs inside the disc changer and to find out, it will be necessary to inspect the contents of each tray.
Another known type of disc changer has a number of sub-trays arranged on a main tray and the main tray is used to transport all the sub-trays to a disc exchange position. However, it is necessary to have a main tray which increases manufacturing costs of the disc changer and loading and replacement of disc are still inconvenient. Further, returning of each tray to its standby position within the casing is inefficient.
Some disc changers include a “Disc Check” function which allows a number of trays to be ejected at different distances away from the casing so that the trays partially overlap each other. This allows the content of the trays to be checked. However, this method is suitable only if the disc changer has a few trays and further, such a function does not allow discs to be loaded/replaced.
Further, in the conventional disc changers mentioned above, when the trays are at the standby position waiting to carry a selected disc to a position for reproducing/recording operation, the tray is engaged with a tray drive gear train, and kept in this position only by friction force of the gear train engagement and a tension of a motor belt. Consequently, the trays are not held securely and misalignment of the trays can occur if the disc changer is transported when the trays are in such a position.
If a locking device is provided to lock all the trays, an additional driving source is needed to unlock the locking state prior to drive the trays. In general, a complicated design is needed to lock the trays. As a locking device in a conventional disc changer usually needs some time to activate the locking function, a shifting of the tray from its standby position easily happens during the tray “non-lock” period. This problem is exacerbated when the “non-lock” period is long, and occurs many times during the disc changer operating period.